Currently, in an X-ray image diagnosis, an absorption image in which X-ray attenuation is imaged after an X-ray has passed through an object is used. On the other hand, an X-ray is a kind of electromagnetic waves, and attention is paid to the wave nature of X-rays, and attempts to image phase change of the X-rays after passing through an object have been recently made. These are called absorption contrast and phase contrast, respectively. The imaging technique using this phase contrast is considered to be more sensitive to soft tissues of a human body, which contains a lot of light elements, because the technique has higher sensitivity to light elements than a conventional absorption contrast.
However, since conventional phase contrast imaging techniques have required use of a synchrotron X-ray source or a minute focus X-ray tube, it has been thought that practical use in general medical facilities is difficult because the former requires a huge facility and the latter is unable to secure sufficient X-ray dose to photograph a human body.
In order to solve this problem, an X-ray image diagnosis (Talbot system) using an X-ray Talbot-Lau interferometer capable of acquiring a phase contrast image using an X-ray source used in medical practice has been conventionally expected.
In the Talbot-Lau interferometer, as shown in FIG. 3, a G0 lattice, a G1 lattice, and a G2 lattice are arranged between a medical X-ray tube and an FPD, respectively, and refraction of X-rays by a subject is visualized as moire fringes. X-rays are irradiated in the longitudinal direction from the X-ray source arranged in an upper portion, and reach an image detector through G0, a subject, G1, and G2.
As a method of manufacturing a lattice, for example, a method in which a silicon wafer having high X-ray transparency is etched to provide lattice-shaped recesses and a heavy metal having high X-ray shielding properties is filled therein is known.
However, with the above-described method, it is difficult to increase the area due to the size of an available silicon wafer, restrictions on an etching apparatus, or the like, and an object to be photographed is limited to a small part. It is not easy to form a deep recess in a silicon wafer by etching, and it is also difficult to evenly fill a metal up to the depth of the recess, and therefore, it is difficult to fabricate a lattice having a thickness enough to sufficiently shield X-rays. For this reason, particularly under high-voltage photographing conditions, X-rays pass through such a lattice, resulting in failure to obtain a favorable image.
On the other hand, it is also considered to adopt a lattice-shaped scintillator having a lattice function added to a scintillator constituting an image detector.
For example, “Structured scintillator for x-ray grating interferometry” (Paul Scherrer Institute (PSI)), Applied Physics Letter 98, 171107 (2011) discloses a lattice-shaped scintillator in which a groove of a lattice fabricated by etching a silicon wafer is filled with a phosphor (CsI).
However, in the above method, since a silicon wafer is used as in the above-described method of manufacturing a G2 lattice, problems caused by a silicon wafer such as constraints of the area of the wafer and difficulty in thickening the wafer are not improved. Furthermore, a new problem that emission of CsI attenuates due to repeated collisions on a wall of a silicon lattice, whereby the luminance decreases has been brought about.